The present invention relates to a detector for monitoring the passing of particles, such as seeds and the like, through a conduit, for the purpose of counting the number of particles passing through the conduit or of monitoring whether or not the particles are passing through the conduit.
In some agricultural apparatus such as mechanized seeders, it is desirable to detect whether seeds are transported (either by gravity or air pressure) to the seeder discharge nozzle with appropriate spacing so as to be deposited in a furrow at a desired relative distance and with a predetermined number of seeds dropped in a given area or within a predetermined time. Mechanized seeders are, therefore, often provided with some detection means for indicating whether the seeds are flowing, or whether some obstruction in the seeder pipe or line has interrupted the flow of seeds to the ground.
Seed flow detectors heretofore used in mechanized seeders are of the optical type. They consist generally of a light source disposed on one side of a conduit through which the seeds are caused to flow one by one and of a photo-cell diametrically disposed relative to the light source, such that the light beam from the light source is interrupted by each seed passing through the condiut, with the photo-cell providing an output signal corresponding to the passage of each seed. It is readily apparent that when operating in a dusty ambient, as is generally the case when seeding a field, and when a certain amount of dust is mixed with the seeds, the efficiency and sensitivity of an optical detector is subject to rapid deterioration unless the light source, the lenses and the photo-cell are subjected to frequent dismantling and cleaning operations. In addition, as each seed must obturate the light beam in order to be detected, such devices cannot be readily made to operate with seeds of different diameters. In other words, when large seeds, such as corn seeds, for example, are used, a conduit of relatively large diameter can be used as long as the seed is caused to be translated substantially along the axis of the conduit, such as to cause a sharp signal at the photo-cell as a result of the seed interrupting all or most of the light beam. However, when smaller seeds are being planted, for example of the order of 3 or 4mm in diameter, it is necessary to replace the relatively large diameter conduit with a small diameter conduit in order to provide a complete occultation of the light beam for obtaining a correct and discrete signal at the output of the photo-cell.
The inconveniences of such conventional optical detectors are readily apparent. A variety of adaptors of different sizes, each conforming to a narrow seed size range, must be used interchangeably, and the use of relatively small throat conduits is often the cause of jamming, such that the detector becomes the cause of the problems it is intended to detect.
Such inconveniences and disadvantages are eliminated by the present invention which provides a particle flow detector capable of accurately detecting and monitoring the flow of particles, such as seeds, through a conduit, irrespective of the size of the particles, by means of a single detector of universal use without adaptors.